Mesh bags are used to package many different products, for instance, children""s toys, small hardware items, flower bulbs, nuts, fruits and vegetables. Plastic bags made with thermal sealable films (both solid and perforated) are also used to package many of these same items. Mesh bags and perforated film bags allow air to flow through the package. Perishable items such as flower bulbs, nuts, fruits, and vegetables are often packaged in mesh or perforated film because they benefit from the airflow.
Vertical form, fill and seal machines are widely used in the packaging industry. They are widely used because they reduce packaging costs, especially labor costs associated with loading or filling premade bags.
Thermoplastic films, both solid and perforated, have been widely used on vertical form, fill, and seal machines for more than 20 years. Mesh materials have generally not been used on vertical form, fill, and seal machines because they are difficult to process on vertical form, fill, and seal equipment.
Typical mesh materials have a significantly higher degree of open air space between strands (openness) than do perforated films. This is true because typical mesh films are composed of thin strands. This is also true because there is a limit to the size and number of perforation holes that can be used before a perforated film loses its tensile strength, tear resistance, and dimensional stability. For example, a typical 10 lb. plastic bag having a length of 18xe2x80x3 and a width of 10xe2x80x3 for fresh whole potatoes might have 12 holes punched for ventilation approximately 0.375xe2x80x3 diameter. This is equivalent to 0.4% is the surface area of the plastic film on both-sides of the bag. Whereas a mesh material such as the preferred CLAF mesh is at least 50% open. The resultant step change in openness for mesh materials significantly increases airflow through the mesh package compared to a perforated film package.
The thin strands of typical mesh materials also reduce the surface area inside the package where moisture and condensation can be trapped and collect. Entrapped moisture and condensation inside the package are generally believed to increase spoilage and/or decrease shelf life for most perishable items, particularly whole potatoes and onions packed fresh or from storage.
The combination of increased airflow through the package is and reduced entrapment of moisture inside the package is desired by most packinghouse operators, distributors, and marketers of perishable fruit and vegetables.
Heretofore, the use of mesh materials on vertical form-fill-seal machines has been limited due to concerns about heat seal failures and overall package integrity. The most common failures are in either (1) the mesh-to-mesh transverse fin seals, and/or (2) the mesh-to-mesh longitudinal lap (or fin) seals. Failures of mesh-to-mesh heat seals are common in the predominant package weights ranging from one pound to ten pounds. In the majority of attempts to use mesh materials on vertical form-fill-seal machines, the package either fails at or adjacent to the transverse fin seal, at or adjacent to the longitudinal lap (or fin) seal, or both. The primary reason for mesh-to-mesh heat seal failures is the lack of an adequate and consistent mass of thermal sealable plastic material in the desired heat seal area.
Although there are distinct advantages to the use of mesh materials for such packages, for many of the above-described reasons, perforated films are typically chosen over mesh for use on vertical form-fill-seal machines when perishable items are being packed.
The grower-shippers and packing facilities that package perishable items have also imposed additional demands for increased packing and filling speeds for pre-made bag filling equipment and automated form-fill-seal packing equipment. In either case, filling premade bags or filling on vertical form, fill, and seal machines, the larger the fill opening for the items to be packed, the greater the filling speed.
Typically, the length of a bag is greater than its width. That being the standard, there is an advantage to filling the bag through the side as opposed to filling through the top. Regardless of the filling method employed (manual, semi-automatic, or fully automatic) the vast majority of all bags are filled through the top of the bag, thus the 10 opening size for placing articles in the bag is limited by the top circumference dimension of the premade bag or vertical form, fill, and seal package. Thusly, the speed of packing is also limited.
Fox U.S. Pat. No. 6,190,044 indicates examples of typical premade bag sizes indicating horizontal (width) and vertical (length) dimensions of the side walls (sides) for various produce weights as follows:
It is clear from the cross sectional area that the openings for filling through the sides are significantly greater the openings for filling top. Those skilled in the art of operating packaging equipment would easily recognize the advantages of being able to automatically fill packages with articles through the larger side opening of the package rather than through the smaller top opening of the package.
Grower-shippers and packing facilities that package perishable items have also imposed additional demands on packing equipment manufacturers for reduced equipment cost, increased packing and filling speeds, increased efficiency, increased flexibility, and reduced waste during the packing processes. This is true for packing machines designed and used for packing pre-made bags, as well as for vertical form, fill, and seal 1 packing machines.
In recent years, particularly in Europe, new vertical form, fill, and seal machines designed to run mesh materials have been introduced to the market by Pannekeet Machine Techniek of The Netherlands, Sorma Netpack of Italy, and Affeldt Verpackungsmaschinen GmbH of Germany. For the most part, these are machines that are designed for the primary purpose of running mesh with large labels front and back, the use of labels being advantageous to reinforce the mesh-to-mesh transverse heat seals. The fact that they require large labels, however, adds significant cost to the final package. There is also the burden of added capital investment for the packing house operator if he has to purchase special vertical form, fill and seal machines designed primarily to run mesh material only.
WO9914121 (EP 0 677 450 A1) is directed to the utilization of a mesh web on vertical form, fill, and seal machines made by Pannekeet Machine Techniek of The Netherlands and Affeldt Verpackungsmaschinen GmbH of Germany specifically for improved packaging of perishable items. WO9914121 (EP 0 677 450 A1) provides that the top and bottom mesh-to-mesh heat seals of the vertical form, fill, and seal package are reinforced by positioning a large film label on both the front and back of the package sandwiching a mesh tube in-between. The front and back labels run the full length and nearly the full width of the lay-flat package. Aside from advertising, the primary purpose of the front and back label is to reinforce and prevent the top and bottom heat seals from failing. While this method may reduce heat seal failures typical of most mesh-to-mesh seals, it falls short because its advantages are offset by the following deficiencies:
(1) the bag must be filled through the narrow top opening; thereby, limiting filling speeds;
(2) the finished bag must be gusseted on both sides in order to eliminate any mesh-to-mesh transverse direction fin seals top and bottom that would likely fail in most practical applications over 1.0 lb.;
(3) the front and back label panels dictate the finished bag width;
(4) the finished bag requires very large labels front and back in addition to the tube of mesh material; thereby, increasing the total packaging materials required by as much as 60% to 70% as compared with alternative packages for the same application, for example Fox 6,190,044 81; and,
(5) the finished bag cost is significantly greater than alternative premade bags made for the same purpose, for example Fox 6,190,044 B1.
Likewise, Sorma Netpack EP 0 788 974 A3 is also directed to the utilization of a mesh web on-vertical form, fill, and seal machines for improved packaging of perishable items. EP 0 788 974 A3 requires that a pre-pared mesh-film web be utilized consisting of five parts, three parts label (comprising the front and back label panels of the bag) and two parts mesh (comprising the side gussets of the bag) This web can only be processed on a vertical form, fill, is and seal machine specifically designed to run this pre-pared mesh-film web. The bag must be formed by forming a mesh gusset on both sides of the bag by tucking a substantial part, apparently 90% or more, of the mesh material between the front and back label panels on both sides of the bag prior to transverse heat sealing. Like EP 0 677 450 A1, EP 0 788 974 A3 utilizes large film labels front and back to sandwich the mesh between the label panels in order to achieve sufficient heat seal strength of the top and bottom transverse seams of the bag. While this method reduces heat seal failures typical of most mesh-to-mesh seals, it falls short because its advantages are offset by the following deficiencies:
(1) the bag must be filled through the narrow top opening; thereby, limiting filling speeds;
(2) the finished bag must be gusseted on both sides in order to preclude mesh-to-mesh transverse direction fin seals top and bottom that would likely fail in most practical applications over 1.0 lb.;
(3) the front and back label panels dictate the finished bag width;
(4) the back label consists of two parts that must be heat sealed longitudinally in the center of the back label panel thereby interfering with the printing of the backside label; and,
(5) the finished bag cost is significantly greater than alternative premade bags made for the same purpose, for example Fox U.S. Pat. No. 6,190,044 B1.
Madderom U.S. Pat. No. 6,105,908 is directed to the utilization of a pre-pared mesh web based upon Rusert-Antonacci patent application dated Sep. 22, 1998, Ser. No. 09/158,307. Madderom U.S. Pat. No. 6,105,908 is directed to the utilization of a pre-pared mesh web with a plurality of sequentially spaced filler strips on vertical form-fill-seal equipment for improved packaging of perishable items. Madderom U.S. Pat. No. 6,105,908 directs that a pre-pared web consisting of a pre-printed fixed length label and precisely sequentially spaced thermoplastic filler strips be applied to a 100% mesh web. The thermal sealable filler strips must be precisely located and sequentially spaced on the pre-pared mesh web at the exact length of the pre-printed label applied to the 100% mesh web. If done correctly, the pre-pared web will process on a vertical form, fill, and seal machine in such a manner that the thermal sealable filler strips are located precisely in the same location as the transverse side heat seals of the finished bag. To date, Madderom U.S. Pat. No. 6,105,908 has not been economically or commercially viable and falls short because its advantages are offset by the following deficiencies:
(1) the process to make the pre-pared web is capital intensive
(2) the process to make the pre-pared web requires special proprietary equipment be purchased in order to produce the pre-pared web;
(3) the process to make the pre-pared web requires special component materials because:
a. the mesh web must have very high tensile strength and low elongation properties to insure the precise location and sequential spacing of the thermal sealable filler strips within approximately +/xe2x88x92 0.125xe2x80x3;
b. the pre-printed label applied to the mesh web must also have very high tensile strength and low elongation properties to insure the precise location and sequential spacing of the thermal sealable filler strips; and,
c. the thermal sealable filler strips have to be a special blend of metallocine Linear Low Density Polyethylene (LLDPE) in order for the process and the finished bag to be successful;
(4) the finished pre-pared web can only be used for a specific predetermined bag size on the vertical form, fill, and seal machine; and,
(5) the finished bag cost is significantly greater than alternative premade bags made for the same purpose, for example Fox U.S. Pat. No. 6,190,044 B1.
The present invention solves the above-described deficiencies within the known prior art by providing for the use of a pre-prepared mesh-film web on conventional form, fill and seal machines. According to the present invention, the pre-prepared mesh-film web is made up of approximately 50% thermal sealable plastic mesh and approximately 50% unprinted or printed film that can be either solid or perforated. The pre-prepared mesh-film web may be processed on conventional vertical form-fill-seal equipment without the need for major modifications or special equipment added to the machine, for instance, label unwinds for the front and back labels. The items may be placed in the bag through the side or the top of the bag.
The prepared mesh-film web may be printed or unprinted prior to being processed on the vertical form-fill-seal packing machine. The majority of vertical form-fill-seal machines have the ability to advance an unprinted continuous web a predetermined length as it is being processed through the vertical form, fill, and seal machine. This enables the operator adjust bag length at any time by resetting that criteria on the control panel. Likewise, the majority of vertical form, fill, and seal machines have the ability to print a continuous web while the web is being processed. This is typically done in-line prior to introduction to the forming mandrel and subsequent formation of a tube. Vertical form-fill-seal machines also enable the operator to process a printed continuous web to make a bag at a predetermined length in accordance with the bag printing or graphics. Thus, the combined options of being able to (1) process a pre-pared printed mesh-film web or (2) print an unprinted pre-pared mesh-film web in-line and (4) change bag length at any time on the unprinted pre-pared mesh-film web provides the vertical form, fill, and seal operator the ability to run a multitude of bag designs and bag sizes without having to change the unprinted pre-pared mesh-film web.
Different types of bags can be formed on different types of vertical form, fill and seal machines by modifying the specific configuration of the pre-prepared mesh-film web of the present invention for the particular package requirements or by modifying the specific configuration of the vertical form, fill, and seal machine.
For example, in some applications, it may be desirable to provide a thermal sealable zipper tape applied during the form, fill and seal process as the longitudinal fin seal is formed, and, thereafter, thermally attaching each side of the tape to the respective free longitudinal edges of the pre-pared mesh-film web.
The primary features and advantages of the invention will be apparent to those skilled in the art upon inspecting the following drawings and description thereof. Importantly, the inventive pre-pared mesh-film webs and the inventive mesh-film bags derived from these webs can be made with relative ease and without any special modifications on commercially available vertical form, fill, and seal equipment.